Liquid crystal display elements are used for not only watches and calculators, but also various electrical equipment for foods, various measuring instruments, automobile panels, word processors, electronic notebooks, printers, computers, televisions, clocks, advertisement display boards, and the like. Typical examples of liquid crystal display systems include twisted nematic (TN) type systems, super twisted nematic (STN) type systems, dynamic light scattering (DS) type systems, guest and host (GH) type systems, in-plane switching (IPS) type systems, optically compensated birefringence (OCB) type systems, electrically controlled birefringence (ECB) type systems, vertically aligned (VA) type systems, color super homeotropic (CSH) type systems, and the like. In addition, examples of driving systems include static driving, multiplex driving, simple matrix systems, and active matrix (AM) systems driven by thin film transistors (TFT), thin film diodes (TFD), and the like.
Among these, in particular, display systems such as IFS type systems and VA type systems, using AM driving are used for display elements which are melted at a high speed and a high viewing angle, for example, televisions, or the like.
Nematic liquid crystal compositions used for these display systems are required to be driven at a low voltage and to have high speed responsiveness and a wide operating temperature range. That is, it is required that the absolute value of Δε be large, the viscosity (η) be low, and the nematic phase-isotropic liquid phase transition temperature (Tni) be high. In addition, from the setting of Δn×d which is the product of the refractive index anisotropy (Δn) and the cell gap (d), it is necessary to adjust Δn of the liquid crystal composition to an appropriate range in accordance with the cell gap. In addition, in the case of applying the liquid crystal display element to a television or the like, since high-speed responsiveness is emphasized, a liquid crystal composition having a low viscosity (η) and small γ1 is required.
In addition to the requirements for the physical properties of these liquid crystal compositions, liquid crystal compositions used for liquid crystal display elements are required to be stable against external stimuli such as moisture, air, heat, and light. When the stability against external stimulation is impaired, display defects such as burn-in and display unevenness occur in the liquid crystal display element. In order to obtain a liquid crystal composition and a liquid crystal display element which do not cause or are unlikely to cause display defects such as burn-in and display unevenness, it is considered that a high voltage holding ratio (VHR) is indispensable and, for that purpose, it is known that a high VHR can be maintained by adding an antioxidant, an ultraviolet absorber, or a light stabilizer to the liquid crystal composition (refer to PTLs 1 to 3).
From the above, there is a need for a liquid crystal composition which achieves a high VHR while satisfying the requirements of the physical properties of the liquid crystal composition and, to fulfill this need, there is a demand for novel antioxidants, ultraviolet absorbers, or light stabilizers which suppress decreases in the VHR.